FIG. 7 shows a configuration of a conventional magnetic recording/reproducing apparatus necessary for recording, FIGS. 8 and 9 show operational illustrations under recording, FIG. 10 shows a configuration of a conventional recording/reproducing apparatus necessary for reproducing, and FIGS. 11 and 12 show operational illustrations under reproducing.
The configuration of the magnetic recording/reproducing apparatus necessary for recording is provided with analog-signal processing means 101, digital-signal processing means 102, modulating means 103, recording-amplifying means 104, a head cylinder 106, switching means 105, and controlling means 107.
The analog-signal processing means 101 applies analog processing and digital conversion to a received video input signal. The digital-signal processing means 102 compresses the data digitized by the analog-signal processing means 101 and adds an error correction code to the data. The modulating means 103 performs the modulation for recording the digital data compressed and provided with an error correction code on a recording tape α. The recording-amplifying means 104 amplifies an output of the modulating means 103. The head cylinder 106 records an output of the recording-amplifying means 104 in the recording tape α. The switching means 105 switches whether to supply an output of the recording-amplifying means 104 to right or left head of the head cylinder 106. The controlling means 107 controls operations of the above configuration necessary for recording.
FIG. 8 is an operational illustration under recording in the case of a compressibility constituted of 10 tracks per frame on the recording tape α, in which symbols denote the following signals.
Symbol (8-a) denotes a frame signal included in a video input signal. Symbol (8-b) denotes a signal-processing H.SW signal for recording data in the recording tape α at a cycle five times larger than that of the frame signal (8-a). Symbol (8-c) denotes a modulated output that is an output of the modulating means 103. Symbol (8-d) denotes the same-cycle H.SW signal synchronizing with the SW signal (8-b), which controls switching by the switching means 105 and rotation of the head cylinder 106. The half cycle of the H.SW signal (8-d) shows one track on the recording tape α. Symbol (8-e) denotes a recording head L or R of the head cylinder 106 switched by the switching means 105. Symbol (8-f) denotes a record signal recorded in the recording tape α. Symbol (8-g) denotes a conceptual illustration of tracks and a frame recorded in the recording tape α.
FIG. 9 is an operational illustration under recording in the case of a compressibility constituted of five tracks per frame on the recording tape α, in which symbols denote the following signals.
Symbol (9-a) denotes a frame signal included in a video input signal. Symbol (9-b) denotes a signal-processing H.SW signal that is set to a cycle five times larger than that of the frame signal (9-a) synchronously with the frame signal (9-a). The signal-processing H.SW signal (9-b) shows one track on the recording tape α of the head cylinder 106. Symbol (9-c) denotes an output (modulated output) of the modulating means 103. Symbol (9-d) denotes an H.SW signal having the same cycle as the SW signal (9-b) synchronizing with the signal (9-b), which controls rotation of the head cylinder 106. The half cycle of the H.SW signal (9-d) shows one track on the recording tape a. Symbol (9-e) denotes an H.SW2 signal for switching heads of the head cylinder 106. Symbol (9-f) denotes a recording head L or R′ of the head cylinder 106 switched by the switching means 105. Symbol (9-g) denotes a record signal recorded in the recording tape a. Symbol (9-h) denotes a conceptual illustration of tracks and a frame recorded in the recording tape a.
The configuration of the magnetic recording/reproducing apparatus necessary for reproducing is provided with reproducing-amplifying means 111, demodulating means 112, digital-signal processing means 113, analog-signal processing means 114, and controlling means 115.
The reproducing-amplifying means 111 amplifies a reproduction signal fetched from the recording tape a through the head cylinder 106 and switching means 105. The demodulating means 112 demodulates a reproduction signal. The digital-signal processing means 113 performs extension and error correction. The analog-signal processing means 114 outputs a video signal to an external unit. The controlling means 115 controls operations of the above configuration necessary for reproducing.
FIG. 11 is an operational illustration under reproducing in the case of a compressibility constituted of ten tracks per frame on a recording tape, in which symbols denote the following signals.
Symbol (11-a) denotes a frame signal for reproducing. Symbol (11-b) denotes an H.SW signal which controls the rotation of the head cylinder 106 and whose half cycle shows one track on the recording tape α. Symbol (11-c) denotes a reproducing head L or R of the head cylinder 106 switched by the switching means 105. Symbol (11-d) denotes a reproduction signal recorded in the recording tape a. Symbol (11-e) denotes a signal-processing H.SW signal that has the same cycle as the H.SW signal (11-b) synchronizing with the H.SW signal (11-b). In the case of this example, the H.SW signal (11-b) and signal-processing H.SW signal (11-e) are set to a cycle five times larger than that of the frame signal (11-a). Symbol (11-f) denotes an reproduced and amplified output supplied from the reproducing-amplifying means. Symbol (11-g) denotes a conceptual illustration of tracks and a frame recorded in the recording tape α.
FIG. 12 is an operational illustration under reproducing in the case of a compressibility constituted of five tracks per frame on a recording tape, in which symbols denote the following signals.
Symbol (12-a) denotes a frame signal for reproducing. Symbol (12-b) denotes an H.SW signal which controls the rotation of the head cylinder 106 and whose half cycle shows one track on the recording tape α. Symbol (12-c) denotes an H.SW2 signal for switching heads of the head cylinder 106. Symbol (12-d) denotes a reproducing head L or R′ of the head cylinder 106 switched by the switching means 105. Symbol (12-e) denotes a reproduction signal recorded in the recording tape α. Symbol (12-f) denotes a signal-processing H.SW signal that is set to the same cycle synchronizing with the H.SW signal (12-b). Moreover, in the case of this example, the H.SW signal (12-b) and signal-processing H.SW signal (12-f) are set to a cycle five times larger than that of the frame signal (12-a). Symbol (12-g) denotes a reproduced and amplified output supplied from the reproducing-amplifying means 114. Symbol (12-h) denotes a conceptual illustration of tracks and a frame recorded in the recording tape α.
Operations of the magnetic recording/reproducing apparatus having the above configuration are described below. In this case, the following two cases are described as examples: a case of realizing the operation for recording/reproducing a video input signal of the broadcasting mode NTSC in accordance with the track division of ten tracks per frame which is the standard of a general digital video signal and a case of realizing the operation for recording/reproducing the video input signal in accordance with the track division of five tracks per frame purposing long-time recording/reproducing.
First, the recording operation conforming to ten tracks per frame is described below. A video input signal supplied from an external unit is input to the analog-signal processing means 101 in which the pedestal level of the video input signal is fixed to a certain level to divide the signal into a brightness signal, a color signal, and a color-difference signal. Then, the video input signal to which the above processing is applied is converted to a digital signal. In this case, the analog-signal processing means 101 generates the frame signal (8-a) in accordance with the video input signal and supplies the signal (8-a) to the digital-signal processing means 102 and controlling means 107.
The frame signal (8-a) is generated to establish the operational timing between the digital-signal processing means 102 and analog-signal processing means 101 or the operational timing between a mechanism section (such as the switching means 105 or head cylinder 106) and the analog-signal processing means 101.
The controlling means 107 to which the frame signal (8-a) is input generates the signal-processing H.SW signal (8-b) showing the head switching timing of the head cylinder 106 in accordance with the frame signal (8-a) and supplies the signal (8-b) to the modulating means 103 in order to realize more minute timing control. Moreover, the controlling means 107 generates the H.SW signal (8-d) serving as a criterion of a head revolving speed and supplies the signal (8-d) to the head cylinder 106 and switching means 105. The H.SW signal (8-d) and signal-processing H.SW signal (8-b) are set to the same-cycle signals synchronizing with each other as described above. Frequencies (revolving speeds) of the signal-processing H.SW signal (8-b) and H.SW signal (8-d) will be described later.
A digital video signal output from the analog-signal processing means 101 is compressed and provided with an error correction code by the digital-signal processing means 102, and then modulated so as to have an energy distribution corresponding to the characteristic of the recording tape α by the modulating means 103.
In this case, the modulated output (8-c) which is an output of the modulating means 103 is set to an output corresponding to the cycle (frequency) of the frame signal (8-a). That is, in the case of the broadcasting mode NTSC, the frequency of the frame signal (8-a) becomes 29.97 Hz. Therefore, by setting frequency of the signal-processing H.SW signal (8-b) to 149.85 Hz which is a frequency five times larger than the frequency of the frame signal (8-a), the modulated output (8-c) is set to an output suitable for the track division of ten tracks per frame.
A recording current is set to the modulated output (8-c) so that the maximum performance of the recording tape α can be shown by the recording-amplifying means 104 and then the modulated output (8-c) is supplied to the switching means 105. The switching means 105 performs the following switching in accordance with the frequency of the H.SW signal (8-d). That is, the switching means 105 controls switching so as to alternately supply the modulated output (8-c) to the heads L and R (provided for the radius-directional both ends of the periphery of the head cylinder 106) as shown by the recording head (8-e). Moreover, the switching means 105 makes the switching cycle synchronize with the half cycle of the H.SW signal (8-d).
The above switching operation is performed by the switching means 105 and the revolving speed of the head cylinder 106 is made to synchronize with the H.SW signal (8-d). That is, the H.SW signal (8-d) serves as a rotational criterion of the head cylinder 106 and its half cycle corresponds to one track {recording assignment of one head L (R)}. By writing the modulated output (8-c) in the recording tape a under the above state, the output (8-c) is recorded in the recording tape a as the record signal (8-f) at a cycle five times larger than that of a video input signal.
Then, the recording operation at five tracks per frame is described below. A video input signal supplied from an external unit is input to the analog-signal processing means 101 in which the pedestal level of the video input signal is fixed to a certain level, and then divided into a brightness signal, a color signal, and a color-difference signal. Then, the video input signal to which the above processing is applied is converted to a digital signal. In this case, the analog-signal processing means 101 generates the frame signal (9-a) in accordance with the video input signal and supplies the signal (9-a) to the digital-signal processing means 102 and controlling means 107. The frame signal (9-a) is generated to establish the operational timing between the digital-signal processing means 102 and analog-signal processing means 101 or the operational timing between a mechanism section (such as the switching means 105 or head cylinder 106) and the analog-signal processing means 101.
To perform more minute timing control, the controlling means 107 to which the frame signal (9-a) is input generates the signal-processing H.SW signal (9-b) showing one track on the recording tape α of the head cylinder 106 in accordance with the frame signal (9-a) and supplies the signal (9-b) to the modulating means 103. Moreover, the controlling means 107 generates the H.SW signal (9-d) serving as the criterion of a head revolving speed and the H.SW2 signal (9-e) for switching heads of the head cylinder 106 and supplies the signals (9-d) and (9-e) to the head cylinder 106 and switching means 105. The H.SW signal (9-d), H.SW2 signal (9-e), and signal-processing H.SW signal (9-b) are set to the same-cycle signals synchronizing with each other as described above. Frequencies (revolving speeds) of the signal-processing H.SW signal (9-b), H.SW signal (9-d), and H.SW2 signal (9-e) will be described later.
A digital video signal output from the analog-signal processing means 101 is compressed and added with an error correction code by the digital-signal processing means 102 and then, modulated so as to have an energy distribution corresponding to the characteristic of the recording tape a by the modulating means 103.
In this case, the modulated output (9-c) which is an output of the modulating means 103 is set to an output corresponding to the cycle (frequency) of the frame signal (9-a). That is, in the case of the broadcasting mode NTSC, the frequency of the frame signal (9-a) becomes 29.97 Hz. Therefore, by setting the frequency of the signal-processing H.SW signal (9-b) to 149.85 Hz which is a frequency five times larger than that of the frame signal (9-a), the signal (9-b) is set to the modulated output (9-c) corresponding to only one of the first-half cycle and second-half cycle constituting one cycle of the signal-processing H.SW signal (9-b). The modulated output (9-c) thus generated becomes an output suitable for the track division of five tracks per frame.
The recording-amplifying means 104 sets a recording current to the modulated output (9-c) generated as described above. This setting is established so as to show the maximum performance of the recording tape α. After this setting is established, the modulated output (9-c) is supplied to the switching means 105. The switching means 105 performs the following switching in accordance with the frequency of the H.SW2 signal (9-e). That is, the switching means 105 controls switching so as to alternately supply the modulated output (9-c) to the heads L and R′ (provided for the radius-directional one side of the periphery of the head cylinder 106) as shown by the recording head (9-f). Moreover, the means 105 makes the switching cycle synchronize with the half cycle of the SW2 signal (9-e).
The above switching operation is performed by the switching means 105 and the revolving speed of the head cylinder 106 is made to synchronize with the H.SW signal (9-d). That is, the H.SW signal (9-d) serves as a rotational criterion of the head cylinder 106 and one turn of the cylinder 106 corresponds to one track {recording assignment of one head L (R′)}. One turn of a head of the head cylinder 106 corresponds to one track. Therefore, when recording all tracks by one head, adjacent tracks on the recording tape a may be simultaneously reproduced under reproducing and thus, one track cannot be correctly reproduced. Therefore, it is necessary to divide heads into L and R′ and record data by providing an azimuth angle for each track. The H.SW2 signal (9-e) shows one turn of the head cylinder 106. Because one turn of the head cylinder 106 corresponds to one track, the tape feed rate is halved in order to equalize the track width on the recording tape a compared to the case of ten tracks per frame. Under the above state, the modulated output (9-c) is recorded in the recording tape a. Thereby, the modulated output (9-c) is recorded in the recording tape a as the record signal (9-g) at a cycle five times larger than that of a video input signal.
Moreover, there is another prior art for the recording operation, in which an output of the recording-amplifying means 104 is supplied to the head cylinder 106 without passing through the above conventional switching means 105. In this case, the modulated output (8-c) which is an output of the recording-amplifying means 104 is not alternately but simultaneously supplied to the heads L and R of the head cylinder 106 in accordance with the cycle of the H.SW signal (8-d) by the switching means 105. In this case, because the head cylinder 106 rotates, either of the heads L and R alternately contacts with the recording tape α. Thereby, the modulated output (8-c) is recorded as the record signal (8-f) at the cycle of a predetermined magnification (five times) of a video input signal similarly to the case of the above conventional example.
Then, the reproducing operation at ten tracks per frame is described below. The controlling means 115 generates the H.SW signals (11-e) and (11-b) respectively showing the head switch timing of the head cylinder 106 in accordance with the frame signal (11-a) generated inside or outside of a unit. Then, the means 115 supplies the H.SW signal (11-e) to the demodulating means 112 and the H.SW signal (11-b) to the head cylinder 106 and switching means 105. The heads L and R of the head cylinder 106 to be switched by the H.SW signal (11-b) operate like the reproducing head (11-c).
Under the above state, the record signal (8-f) of the recording tape α is reproduced by rotating the head cylinder 106. In this case, by making the revolving speed of the head cylinder 106 and the switching cycle of the switching means 105 synchronize with the H.SW signal (11-b), the record signal (8-f) is reproduced in its signal form. That is, as described above, the record signal (8-f) is recorded in the recording tape α as the track division of ten tracks per frame. Therefore, by converting the H.SW signal (11-b) to be supplied to the head cylinder 106 and switching means 105 into a signal having a cycle [149.85 Hz in the case of the broadcasting mode NTSC] five times larger than the cycle of the frame signal (11-a) [29.94 Hz in the case of the broadcasting mode NTSC], the record signal (8-f) is reproduced in a state suitable for the track division (ten tracks per frame) of the signal (8-f) and the reproduction signal (11-d) is supplied to the reproducing-amplifying means 111.
The reproducing-amplifying means 111 amplifies the reproduction signal (11-d) and then, supplies the reproduced and amplified output (11-f) of the signal (11-d) to the demodulating means 112. The demodulating means 112 demodulates the data modulated in accordance with the characteristic of the recording tape α under recording and supplies it to the digital-signal processing means 113. In this case, the demodulating means 112 generates a demodulated output by relating the output to the signal-processing H.SW signal (11-e) [same-cycle signal synchronizing with the H.SW signal (10-b)] and thereby, converts the demodulated output into a signal form of the track division of ten tracks per frame correspondingly to the cycle of the frame signal (11-a).
The digital-signal processing means 113 error-corrects and error-revises a received demodulated output and extends compressed data to supply them to the analog-signal processing means 114. In this case, the digital-signal processing means 113 processes a signal synchronously with the frame signal (11-a) supplied from the controlling means 115.
The analog-signal processing means 114 converts a received output of the digital-signal processing means 113 to an analog signal and outputs the analog signal to a unit outside of the apparatus as a reproduced video signal.
Then, the reproducing operation at five tracks per frame is described below. The controlling means 115 generates the signal-processing signal H.SW signal (12-f) serving as one track on the recording tape of the head cylinder 106, the H.SW signal (12-b) serving as the criterion of a head revolving speed, and the H.SW2 signal (12-c) for switching heads of the head cylinder 106 in accordance with the frame signal (12-a) generated inside or outside of a unit. Then, the means 115 supplies the signal-processing H.SW signal (12-f) to the demodulating means 112, the H.SW signal (12-b) to the head cylinder 106, and the H.SW2 signal (12-c) to the switching means 105. The heads L and R′ of the head cylinder 106 to be switched by the H.SW2 signal (12-c) operate like the reproducing head (12-d). In this case, the tape feed rate is set to ½ the case of ten tracks per frame.
Under the above state, the record signal (9-g) of the recording tape α is reproduced by rotating the head cylinder 106. In this case, the record signal (9-g) is reproduced in its signal form by making the revolving speed of the head cylinder 106 synchronize with the H.SW signal (12-b) and the switching cycle of the switching means 105 synchronize with the H.SW2 signal (12-c). That is, as described above, the record signal (9-g) is recorded in the recording tape α in the form of the track division of five tracks per frame. Therefore, by converting the H.SW signal (12-b) to be supplied to the head cylinder 106 to a signal having a cycle (149.85 Hz in the case of the broadcasting mode NTSC) five times larger than the cycle [29.94 Hz in the case of the broadcasting mode NTSC] of the frame signal (12-a) and generating the H.SW2 signal (12-c) using the switching cycle of the switching means 105 as the one-turn cycle of the head cylinder 106, the record signal (9-g) is reproduced in a state suitable for the track division (five tracks per frame) of the signal (9-g) and the reproduction signal (12-e) is supplied to the reproducing-amplifying means 111.
The reproducing-amplifying means 111 amplifies the input reproduction signal (12-e) and then supplies the reproduced and amplified output (12-g) to the demodulating means 112.
The demodulating means 112 demodulates the data modulated in accordance with the characteristic of the recording tape α under recording and supplies it to the digital-signal processing means 113. In this case, the demodulating means 112 generates a demodulated output correspondingly to the signal-processing H.SW signal (12-f) and thereby, converts the demodulated output to a signal form of the track division of five tracks per frame correspondingly to the cycle of the frame signal (12-a).
The digital-signal processing means 113 error-corrects and error-revises a received demodulated output and extends compressed data to supply them to the analog-signal processing means 114. In this case, the digital-signal processing means 113 processes a signal synchronously with the frame signal (12-a) supplied from the controlling means 115.
The analog-signal processing means 114 converts a received output of the digital-signal processing means 113 to an analog signal and outputs the signal to a unit outside of the apparatus as a reproduced video signal.
A magnetic recording/reproducing apparatus operating as described above has the following problem. That is, as described above, the head configuration of the head cylinder 106 cannot be equalized in the case of recording and generating data in accordance with the track division of ten tracks per frame and in the case of recording and reproducing data in accordance with the track division of ten tracks per frame at further-improved compressibility and therefore, it is necessary to prepare a head corresponding to each case. Moreover, it is necessary to switch tape feed rates and thereby, a configuration of the magnetic recording/reproducing apparatus is complicated and the fabrication cost is increased.
Furthermore, it is necessary to rotate the head cylinder 106 at a high speed of 149.85 Hz. However, to accurately keep the high-speed rotation of the head cylinder 106, a high-accuracy mechanism is necessary and thereby, the fabrication cost of a magnetic recording/reproducing apparatus is increased.
Furthermore, to accurately keep a mechanism for supporting the high-speed head cylinder 106, it is inevitable to require a lot of time for maintenance under operation and this causes the running cost of a magnetic recording/reproducing apparatus to increase.
As described above, because a conventional magnetic recording/reproducing apparatus is expensive, an inexpensive magnetic recording/reproducing apparatus realizing digital recording and reproducing is requested.